The invention relates to a charging device for an electric vehicle.
It is known from the prior art to charge the electrical energy store provided for driving an electric vehicle via a single-phase AC charging system. In this case, single-phase alternating current is supplied from an electrical connection via a charging cable to a corresponding connection on the vehicle side. The alternating current is converted into direct current in the vehicle via a charger, and this direct current is used for charging the electrical energy store.
Conventional electrical connections which are used in private households, for example, already provide a single-phase alternating current, but the power of such connections is limited to 3.7 kW or 16 A at most. Therefore, such connections are not suitable for a so-called high-speed charging function of the electrical energy store in the vehicle, for which a power of 7.4 kW or a current of 32 A is generally required. Although a conventional single-phase electrical connection can possibly be rated for higher powers, in general a change to the installation of the current distribution towards the energy distribution grid of the energy provider is required for this purpose, which is associated with a high degree of complexity.
The document DE 10 2011 007 839 A1 discloses various vehicle charging devices in which the charging of an electrical energy store of an electric vehicle with a single-phase or three-phase alternating current is made possible via an external AC grid connection. Furthermore, the charging devices can be used for DC charging of the electric vehicle.
An object of the invention is to provide a charging device for an electric vehicle with which efficient charging of the energy store of the electric vehicle with single-phase alternating current is made possible in a simple manner.
One embodiment of the charging device, according to the invention, is provided for an electric vehicle which can be driven via an electrical energy store (for example via a battery). The term electric vehicle should in this case be understood broadly and includes any type of motor vehicle which has an electrical energy store for the drive thereof, such as, for example, truly electric vehicles or possibly also hybrid vehicles. The charging device according to the invention comprises a charging interface outside the electric vehicle, which charging interface can be fed at the input by a three-phase alternating current from an external three-phase AC grid and provides a charging current at the output, which charging current can be supplied via a charging cable to the electric vehicle for charging the electrical energy store. Preferably, in this case the charging cable is fixedly connected to the charging interface, i.e. it cannot be removed via a plug connector system. In this case, the charging cable should be considered to be part of the charging device. The term charging interface should be understood broadly here and below and can include, inter alia, a wallbox, a charging station or an EVSE (Electric Vehicle Supply Equipment). In particular, the charging interface can possibly also be part of the charging cable.
The charging device according to one embodiment of the invention is characterized by the fact that the charging interface thereof comprises a converter device for converting the three-phase alternating current into a single-phase alternating current as charging current, wherein the converter device is configured in such a way that a phase load or a phase current on the line phase of the single-phase alternating current is distributed substantially uniformly among the three line phases of the three-phase alternating current. In this case, the invention is based on the knowledge that, with a corresponding charging device, the three-phase alternating current of an AC grid can be used for charging an electric vehicle by being converted into a single-phase alternating current without the phase load being increased non-uniformly only on one phase of the AC grid in the process. As a result, higher currents can be supplied to the electric vehicle, which in turn results in quicker charging of the electrical energy store. Furthermore, in contrast to single-phase charging directly from the external AC grid, the load on the PEN conductor is kept low, as will be illustrated in more detail in the detailed description. The charging device according to one embodiment of the invention thus makes it possible to reduce the reaction on the external AC grid.
The use of a converter device having the above properties for single-phase AC charging of the electrical energy store of an electric vehicle is not known from the prior art. In a preferred embodiment, the converter device comprises an AC-to-DC-to-AC converter (also referred to as DC-link converter), which converts the three-phase alternating current into a direct current and this direct current into a single-phase alternating current.
In a particularly preferred configuration, the converter device is designed for converting a three-phase alternating current with a phase current of (at most) 16 A, i.e. the charging device is suitable for installation in conventional power distribution systems and in particular in power distribution systems in private households. In addition, the converter device is preferably designed for providing a single-phase alternating current with a phase current of (at most) 32 A. As a result, a single-phase AC quick-charging function is made possible for the electric vehicle.
In a further, particularly preferred embodiment, the charging interface comprises a control unit, which can communicate with the electric vehicle for controlling the charging operation of the electrical energy store via a communications line in the charging cable. Such control units are known and generally so-called pilot contacts are used for producing the connection between the control unit and the vehicle via the communications line.
In a further preferred embodiment, the charging interface furthermore comprises an AC-to-DC converter for converting the three-phase alternating current into a direct current as charging current. As a result, the charging interface can also be used additionally for DC charging of the electric vehicle. Preferably, in this case the charging interface comprises a multi-stage switch having a first and at least a second switching stage, which switch is controllable via the control unit, wherein, in the first switching stage, the AC-to-DC converter is electrically connected to the external three-phase AC grid and, in a second switching stage, the converter device according to the invention is electrically connected to the external three-phase AC grid. Possibly, in addition, a further second switching stage can be provided, in which the external three-phase AC grid is connected directly to a three-phase AC connection of the charging interface for providing three-phase alternating current as charging current, whilst bypassing the converter device.
In a further preferred embodiment, the charging interface comprises a plurality of electrical taps, which are connectable or connected, with the same assignment, to electrical lines of the charging cable, wherein at least the line phase and the neutral phase of the single-phase alternating current and grounding are provided via the plurality of electrical taps.
In the case where the charging device also enables the function of DC charging, the plurality of electrical taps furthermore comprises two taps for providing the direct current from the AC-to-DC converter. In a particularly preferred embodiment, in this case the charging device is constructed similarly to those charging devices in the above-cited document DE 10 2011 007 839 A1 which are intended for single-phase AC charging via a single-phase AC grid. In addition, however, the converter device is provided for converting a three-phase alternating current into a single-phase alternating current. Preferably, the plurality of electrical taps furthermore comprises a tap for connection to the communications line described above in the charging cable. The entire disclosure of the document DE 10 2011 007 839 A1 is incorporated by reference in the present application.
In a further configuration of the invention, a three-phase AC connection of the charging interface is connectable directly to the external three-phase AC grid whilst bypassing the converter device. This can be achieved via a corresponding switching device, which is preferably actuated via the above-described control unit.
In a further variant of the invention, in which an AC-to-DC converter is provided for DC charging and the converter device is in the form of an AC-to-DC-to-AC converter, the AC-to-DC converter is a converter stage of the AC-to-DC-to-AC converter when providing a single-phase alternating current as charging current. This can be achieved by a switching device on the output side of the AC-to-DC converter, which switching device is preferably actuated via the above-described control unit.
In a particularly preferred embodiment, the charging interface for charging the electrical energy store of the electric vehicle is provided on the basis of the standard known as International Electrotechnical Commission 62196 (“IEC 62196”).
That is to say that all of the male connector/female connector connections for connecting the charging cable to the vehicle and all of the charging modes of this standard can also be realized in the charging device according to the invention if the corresponding connection or the corresponding charging modes enable single-phase AC charging.
Exemplary embodiments of the invention will be described in detail below with reference to the attached figures, in which:
Other objects, advantages and novel features of the present invention will become apparent from the following detailed description of one or more preferred embodiments when considered in conjunction with the accompanying drawings.